/*
 * Copyright (c) 2013, SRI International
 * All rights reserved.
 * Licensed under the The BSD 3-Clause License;
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 * 
 * http://opensource.org/licenses/BSD-3-Clause
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 
 * Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 
 * Neither the name of the aic-expresso nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.sri.ai.grinder.library.equality.cardinality.direct.core;

import com.google.common.annotations.Beta;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.expresso.api.Symbol;
import com.sri.ai.expresso.helper.Expressions;
import com.sri.ai.grinder.api.RewritingProcess;
import com.sri.ai.grinder.core.AbstractHierarchicalRewriter;
import com.sri.ai.grinder.helper.Trace;
import com.sri.ai.grinder.library.boole.Implication;
import com.sri.ai.grinder.library.equality.cardinality.CardinalityUtil;
import com.sri.ai.grinder.library.equality.cardinality.direct.CardinalityRewriter;

/**
 * Rewriter replacing expression by true or false if it or its negation is implied by the context.
 * 
 * @author braz
 *
 */
@Beta
public class TopImpliedCertainty extends AbstractHierarchicalRewriter implements CardinalityRewriter {
	
	public TopImpliedCertainty() {
	}
	
	@Override
	public String getName() {
		return R_top_implied_certainty;
	}
	
	/**
	 * @see CardinalityRewriter#R_top_implied_certainty
	 */
	@Override
	public Expression rewriteAfterBookkeeping(Expression expression, RewritingProcess process) {
		Expression result = expression;
		
		if (!(expression instanceof Symbol)) {
			if (CardinalityUtil.isFormula(expression, process)) {
				Trace.log("if F is a formula");
				Expression c            = process.getContextualConstraint();
				Expression cImpliesF    = Implication.make(c, expression);
				Expression cImpliesNotF = Implication.make(c, CardinalityUtil.makeNot(expression));
				Trace.log("    if is_tautology(C => F)");
				if (IsTautology.isTautology(cImpliesF, process)) {
					Trace.log("        return true");
					result = Expressions.TRUE;
				} 
				
				if (result == expression) {
					Trace.log("    if is_tautology(C => not F)");
					if (IsTautology.isTautology(cImpliesNotF, process)) {
						Trace.log("        return false");
						result = Expressions.FALSE;
					}
				}
			}
		}

		return result;
	}
}
